Method and instrument for testing eyes



Oct. 12, 1937, A. AMEs. JR Y 2,095,235

I I IETHOD AND INSTRUMENT FOR TESTING EYES Filed Jan. 13, 1934 1.6 Sheets-Sheet 1 Rm rg Oct. 12, 1937.

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METHOD AND INSTRUMENT FOR TESTING EYES Filed Jan; 13, 1934 16 Sheets-Sheet 8 Oct. 12, 1937. A. AMES. JR

I METHOD AND INSTRUMENT FOR TESTING EYES Filed Jan. 13, 1934 I6 Sheets-Shegt 9 hmsem yui Oct. 12, 1937. .A. AMES. JR.

METHOD AND lNSTRUMENT FOR TESTING EYES Filed Jan. 13, 1934 16 Sheets-Sheeflo jwercfpy a aai ezewza Md 1 M? Cs:

Oct. 12, 1937. A. AMES. JR

METHOD AND INSTRUMENT-FOR TESTING EYES Filed Jan. 13, 1934 16 Sheets-Sheet 11 w wmzzi Qct; 12, 1937. A. AMES. JR

METHOD AND INSTRUMENT FOR TESTING EYES Filed Jan. 15, 1934' 16 Sheets-Shed 12 A. AMES. JR METHOD AND INSTRUMENT FOR TESTING EYES Filed Jan. 15, 1934 16 Sheets-Sheet 15 M y W. a 2 J b 5 d m 4 s e I I 0 I. 4

Oct. 12, 1937.

A. AMES. JR

METHOD AND IXSTRUMENT FOR TESTING EYES Filed Jan. 13. 1934 16 Sheets-Sheet 14 M7 WM/ Oct.12 ,1937. M JR 2,095,235

METHOD AND INSTRUMENT FOR TESTING EYES Filed Jan. 13, 1934 16 Sheets-Sheet 15 76 77 h I 1.564- a 6/ f ----/7 -r' l nmllmnrl-l 0a. 12 1937. Am, JR 7 2,095,235

umaob AND INSTRUMENT FOR 'mswme EYES Filed Jan. 13, 1934 16 Sheets-Sheet 16 Patented Oct. 12, 1937 UNITED STATES PATENT OFFICE METHOD AND INS'IEtYILSIENT FOR TESTING Adelbert Ames, Jr., Hanover, N. H., assignor to Trustees of Dartmouth College, Hanover, N. H., a corporation of New Hampshire Application January 13, 1934, Serial No. 706,523

50 Claims.

10 The refractory and muscular defects of the eyes are well known, whereas the more recently investigated image difference defects are discussed, for example, in Patents Nos. 1,933,578 of November 7, 1933 and 1,944,871 of January 30, 15 1934, and also in various publications, for example. in the Journal of the Optical Society of America, volume 22, page '538. Therefore, it will be sufficient to recapitulate that these image difference defects are caused by discrepancies of the ocular images which are sometimes also referred to as retinal images, these terms being used to describe the impression formed in the higher brain centers through the vision of one eye. These ocular images are determinednot only by the properties of the dioptric image that is formed on the retina of the eye butalso by modifications caused by anatomical properties and physiological conditions influencing the transmission of this optical image to these brain centers.

The two ocular images of a pair of eyes may differ in size at the same ratio in all directions (over all size differences) or they may so differ in one direction only (meridional size diiferences) Or they may difier irregularly (asymmetric size 35 differences, or shape, differences). All these differences of the ocular images will be herein shortly referred to as image differences", unless it is specifically stated that only one of these several types of defects, which'may be coexistent, is discussed in any particular instance. Such defects do not only cause great inconvenience but may be the underlying cause of quite serious vis-' ual, nervous, and other disturbances. Eyeglasses for relieving such defects are described and 45 claimed in the above-mentioned application Patent No. 1,933,578, and methods and instruments for examining patients for the purpose of prescribing glasses for all corrigible ocular defects, including image differences, are described in Pat- 50 cut No. 1,944,871.

Conditions which have to do with the size and shape of ocular images are also characterized by the term eikonic". The condition in which size and shape of the ocular images are equal is called 55 "iseikonia", whereasthe condition in which size or shape are unequal is termed aniseikonia, which as above discussed, may be overall or meridional.

It was .found that the prior methods and devices for examining eyes for such defects, although quite effective within their scope, are for certain purposes not suiliciently exact, convenient and adaptable to varying conditions. For

, example, the devices for directly measuring the V refractory characteristics of the eyes simultaneously with the other above-mentioned defects, are not as exact as they might be, for measuring ordinary as well as astigmatic focal lengths. Also,

the indirectly viewed targets, separate for each eye, for evaluating image differences and phorias are not absolutely satisfactory. A precise combination, and cooperation of these optically superimposed target units with the other testing elements of the instrument is diflicult. Especially the unavoidable slight inaccuracies in mechanical details, differences due to heat expansion and contraction, and other causes of slight dimensional variations of the two separate targets causes difliculties since, in order exactly to evaluate the image differences, the test objects presented to each eye must be exactly of the same dimension, and positioned very exactly relative to each other and to the other elements of the instrument.

Therefore, some of the main objects of the present invention are to provide simplified and more exact methods and devices for determining refractory, uscular and image difference defects of the e es; to provide a method for evaluating image di erences which is inherently absolutely accurate and reliable, and test objects or targets of simple, convenient and inexpensive construction for carrying out the new method; to provide methods and means for accurately and conveniently measuring refractory defects 40 of the eyes with an instrument of the type herein referred to; and generally to provide methods, and accurate and yet simple and easily. operable instruments for testing eyes for all corrlgible defects, including refractory,muscular and size difference faults, thereof, whereby, further, the eyes can be tested by accurately reproducing the conditions under which they are actually used in everyday life.

In one aspect, the invention involves, as already mentioned, methods which are inherently accurate for testing image difference andphorla defects and are independent of the mechanical imperfections of test means separately presented to each eye. This object is attained, according to the present invention, by introducing a single element, located in the direct line of vision (that is a line of vision which is not broken or deviated, for example by prisms or mirrors, disregarding, however, the efiect of test elements inserted before the eyes), which presents to each eye the appearance of an object, design, or detail, whose character is rendered non-fusibly different or dissimilar for each eye by suitable means, whereas the spatial arrangement or distribution of the detail is only determined by the directly viewed single element. This single test element is used with an object or objects determining the vergence of the eyes, also referred to as fixation means or fixation mark. According to the present invention, the fixation means is preferably a single, fusible object presented in fixed spatial relationship with the means for determining the uniform spatial arrangement of the non-fusible detail.

Since the presentation of the detail is brought about by a single element, it is evident that the detail must necessarily appear to the eyes as similarly located in space. Its dissimilarity in character may be obtained in various ways as, for example, by making it of different light intensity, or of different colors, as will be described hereinafter. Due to their peculiar. nature, the devices for carrying out the new method for testing imagedifferences (herein referred to for short as size targets, although they permit the evaluation of all above-mentioned size or shape defects, or .all types of fixation disparities, or of any of these defects in combination) can be easily combined with means for testing other eye deficiencies in a manner not possible with the previously described instruments having a distinct image magnitude target for each eye. It is especially possible to combine the new targets with either directly or indirectly viewed apparatus for dioptric tests. They also permit the convenient testing of image differences for comparatively great viewing distances, the use of several, or the same, targets for different inclinations of the line of vision, but also the use of a single target for different distances and therefore convergencies, and for different inclinations of. the line of vision.

Another object of the invention, made possible by thenew method of image difference testing, is to provide a simple way of changing the dissimilar characteristics of the non-fusible object appearances presented to the respective eyes,

from one eye to the other, without changing the spatial arrangement of the appearances. This object can be accomplished according to the new method, because it employs separate instrumentalities for determining the similar spatial arrangement with respect to a fixation means, and

for determining the dissimilar character, respectively, of the appearances.

Another feature of the invention is a new method, and various devices for carrying this method into practice, for determining points conjugate to the retina, that is, the focal length of an eye, for'any desired vergence of the eyes. This method utilizes focusing objects not conveying the imalways appear of the same size, no matter what vice that permits universally reproducible posi-- tioning of the head in a convenient and exact manner.

Still another object of the invention is to provide a simple but exact and efficient method for investigating phorias, and means for carrying out this method.

Instruments according to the invention also include features whose objects are to provide exact and convenient means for correctly positioning the eyes relatively to the instrument, in which position they can then be fixed with the abovementioned head positioning instrumentalities; and to provide means for tilting certain elements of the instrument.

In one embodiment of the invention which will be described herein in detail, a single size target is combined with a single focusing object which, according to the invention, can be virtually positioned in various distances relatively to the target, this embodiment being especially suitable where compactness of the instrument is desired. This embodiment also introduces features whose objects are to provide means for measuring the refractive condition of each eye, at a fixed vergence of the eyes, with a single focusing object, and to provide means which eliminate from one eye the vision of the focusing object seen by the other eye without introducing any irritating or confusing appearances.

Another embodiment according to the invention, also to be described in detail, combines several size targets with indirectly viewed focusing objects, which arrangement permits especially exact and complete measurements. This embodiment includes novel means providing for conveniently and accurately tilting a portion of the instrument, and means for quickly and accurately adjusting the refractory test means or focusing objects for different puplllary distances and vergence angles of the eyes.

In still another aspect, the new method and the new devices for its execution provide for the con comitant evaluation of dioptrlc, muscular and image difference defects, and their interdependency and correlation, by continuously maintaining binocular vision approximating the conditions under which the patient is accustomed to use his eyes. This feature is especially important since it was found that these defects are so closely interrelated that a satisfactory examination and correction of the eyes is only possible by continuously checking the mutual influence of these ocular conditions and of the means for correcting them, thereby maintaining binocular vision as determined by a certain vergence of the eyes.

This and other objects, aspects and features of the invention will become apparent from the following detailed explanation illustrating the genus of the invention with reference to several concrete embodiments thereof. The description refers to drawings, in which Fig. l is a diagram illustrating the general principles of the invention;

Figs. 2, 3, and 4 are diagrammatic targets according to the invention;

- Fig. 5 is a diagrammatlcal side elevation of a plans of size of various modifications of a focusing device according to'the present invention;

Fig. 10 is a diagram illustrating the function of a device according to Figs. 6 to 9, inclusive;

Fig. 11 is a diagram explaining the investigation of astigmatism with the aid of a device accordingto Figs. 6 to 9, inclusive;

Fig.-12 is a front elevation of a focusing device accordingto Fig. 9;

Fig. 13 is a section on line l3--|3 of Fig. 12;

Figs. 14' and 15 are a diagrammatical front elevation and a plan, respectively, of a multiple focusing object;

Fig. 16 is a view similar to Fig. 14 but with the astigmatic images aligned;

Fig. 17 is the front elevation of a focusing device constructed according to Figs. 14 to 16, with the lower portion of the slider omitted;

Fig. 18 is a section on line 18-"! of'Fig. 17;

Fig. 19 is a section on line l9--l9of Fig. 18;

Fig. 20 is a front elevation of a focusing device with selectively adjustable testing object;

Fig. 21 is a section on line ll-2| of Fig. 20;

Fig. 22 is a section on line 22-42 of Fig. 21;

Fig. 23 is a front elevation similar to Fig. 20, but with the cover plate removed;

Fig. 24 is a section on line 26-26 of Fig. 23;

Fig. 25 is a diagram illustrating the operation of an auxiliary lens for use with focusing devices according to the invention;

Fig. 26 is an isometric view of one embodiment of an instrument for carrying out the eye testing method according to the invention;

Fig. 27 is a view of the front side of the test slide shown in Fig. 26;

Fig. 28 is a similar view of the back side of the slide shown in Fig. 27; I

Fig. 29 is a diagrammatic plan view of the instrument shown in Fig. 26;

Fig. 30 is a front elevation of the size target according to Fig. 29 as it appears to the left eye;

Fig. 31 is a similar view of the target as it appears to the right eye; I

Fig. 32 is a front view of the refractive test chart shown in Fig. 26;

.Fig. .33 is a side elevation of another embodiment of an instrument for carrying out the eye testing method according to the invention;

Fig. 34 is a front elevation of the instrument.

shown in Fig. 33;

Fig. 35 is a plan view of the instrument, shown in Fig. 33;

Fig. 36 is a plan view of part of the head rest structure shown in Figs. 33 and 34;

Fig. 3'7- is a plan view of the head rest slide shown in Figs. 33 and 34;

Fig. 38 is a plan view of the head rest bed shown in Figs. 33 and 34, with the sl de removed;

, Fig. 39 is a bottom view of the slide shown in Fig. 37;

Fig. 40 is a section through the head' rest mechanism,'on line 46- 46 of Fig. 39;

Fig. 41 is a section on line ll- M of Fig. 39;

Fig. 42 is a section on line 42-42 of Fig. 33;

Fig.43 is a section through the head rest column on line 43-43 of Fig. 40;

Fig. 44 is a similar section on line 64-44 of Fig. 40;

Fig. 45 is a front view of the instrument foot shown in Figs. 33 and 34;

" Fig. 46 is a front view of the bridge structure of v in Figs. 58 and 59;

Figs. 33 and 34, shown in alignment with the instrument foot of Fig. 45;

Fig. 47 is a section on line 47-41 of Fig. 34, showing the construction of the instrument bridge;

Fig. 48 is a diagram illustrating the mannerin which the bridge structure is moved;

Fig. 49 is a section on line 49-49 of Fig. 35;

Fig. 50 is a front elevation of the size target shown in Figs. 33 and 34 with the test chart in place;

Fig. 51 is a side elevation of the same target;

Fig. 52 is a view similar to Fig.5!) with the chart removed;

Fig. 53 isa view of the screen shown in Figs. 50 and 51; g n

Fig. 54 is a section on line ti t-56 of Fig. 50;

Fig. 55 is a front view of a large size target according to the invention;

Fig. 56 is a back view of the target according to Fig. 55;

Fig. 57 is a section on line ST-51 of Fig. 56;

Fig. 58 is a front elevation of one of the tubular structures shown in Figs. 56 and 57;

Fig. 59 is a side elevation, with the foot in section, on lines 59-59 of Fig. 58, of the tubular structures according to Fig. 58;

Fig. 60 is a plan of the shutter structure shown Fig. 61 is an elevation of a screen structure forming a modification of the shutter shown in Fig. 60; o

Fig. 62 is a section on line 62-62 of Fig. 61;

Fig. 63 is a wiring diagram of the illumination equipment of the instrument shown in Figs. 33 and 34;

Fig. 64 shows a chart used for determining phorias; and

Figs. 65 to 73 are diagrammatical front views of size targets as they appear to eyes under various conditions.

The principles underlying the method and the instruments according to the invention will first be explained by referring to Fig. 1. In this figure, OD and OS are the right eyeand the left eye, respectively, with centers: of rotation CD and CS, respectively, which points are connected by horizontal axis vof rotation h. In order to simplify the diagrammatical' Fig. '1, the light rays are drawn as if the nodal points of the eyes coincided with the centers of rotation, whereas actually the nodal points are, as well known, a certain distance in front of the centers of rotation. C is a point midway between the eyes, from which a horizontal line 0, referred to as normal line of vision, leads to a point F at which the eyes are looking in horizontal direction. F will be referred to as fixation point. The lines s and d from the eyes to the fixation point F are the visual axes of the eyes, and the angle 7 which they subtend "at F is a measure of the convergency of the eyes.

While it may be assumed that these axes are approximately horizontal when the person in question is looking straight ahead at infinite distances (to which a distance of approximately 6 m. is substantially equivalent), they are inclined when the person reads or does other work at close distance, the head being assumed to "remain in the same position. It was found that an inc1ination of the visual axes of about 20 to the horizontal direction, with the. position of the head the same as for distant vision, and a convergence ofthe eyes to a point about 40 cm. from their centers of rotation approximately reproduces this condition of 'near work, which is indicated in Fig.

1 by inclined line of vision I), angle 6=20 and inclined visual axes t and e converging towards fixation point E.

The fixation point F may be provided directly by an object or fixation mark, as for example a dot, ring, letter, or cross painted on a screen in plane A, or indirectly by adjusting indirectly viewed test objects in such a manner that the appropriate line of vision of each eye is established by the virtual image of a test object. For example, a semi-transparent mirror M may provide in axis s an image of object O, and a similar mirror an image of a second object in axis d, which arrangement causes the eyes to converge at F, as at length described in patent No. 1,946,925 of February 13, 1934. Similarly, mirrors represented by reflector N, and objects represented by Q, may be provided for each eye, causing the appearance of fixation point E on a plane K perpendicular to inclined line of vision b.

For purposes of the present invention which utilizes the already mentioned novel method of testing image differences, it is preferable to establish convergence with a fixation object viewed directly by both eyes. Such a single object can be definitely correlated with the single element determining the spatial arrangement of the size target detail, which arrangement assures inherently exact and unchangeable distancing of fixation mark and size target detail. It is, however, understood that either mode of establishing convergence may be employed.

It will be evident that fixation points at various locations (preferably for distance and near vision as above defined) can be obtained either by pro-' viding several directly viewed fixation marks or by optically moving a fixation mark by inserting the proper optical means, as prisms and lenses, between eye and mark, or by appropriately changing the position of mirror and indirectly viewed objects.

For measuring refractory defects, test objects (herein referred to as focusing objects) are provided, which permit the determination of a point conjugate to the retina of the eye, when the eyes are at a certain vergence. objects are preferably of a type, to be described in detail hereinafter, that permits exact determination of their coincidence with the conjugate points, and in addition the determination of astigmatic meridian and astigmatic interval. In order to permit refractory investigations at various positions of the fixation point, focusing objects like 0 and Q of Fig. 1 may be viewed indirectly through transparent mirrors as M and N, and moved along tracks m and n. These tracks should be adjustable, with their mirrors, for different positions of axes s and d, about vertical axes v and to through centers of rotation CS and CD, respectively.

Instead of indirectly viewed focusing objects like 0 and Q, such objects may be provided in the.

direct line of vision of an eye, as indicated at P and R. If such directly viewed focusing objects are used, the vergence of the eyes must be fixed with the aid of indirectly viewed means, or, as a preferred embodiment according to the present invention, a directly viewed fixation mark must permit observation of the focusing object. If one directly viewed focusing object is used for both eyes, it must be arranged to be rotatable about the fixation point, as will be evident from Fig. 1 where P is in the axis of the eye OD, and R in the axis of the eye OS. For various positions of the fixation point, either separate focusing objects Such focusing can be provided, or one object can be differently positioned either actually or virtually by appropriate optical means. Practical means accomplishing these functions will be described hereinafter.

Lenses for optically placing the various test objects at different distances may be inserted at the appropriate points, as for example indicated at G, G and G" of Fig. 1. According to the invention, such lenses may have the further function of making the apparent size of test objects approximately constant and of permitting the convenient reading of distances in diopters from the nodal points, as will be explained in detail hereinafter.

Optical means, as conventional power lenses, prisms, or size changing lenses can be inserted in front of each eye, as indicated in Fig. 1, where, for example, l6 and I1 may be power lenses correcting overall and astigmatic refractory defects, or prismatic glasses, or both, and where l8 and I9 may be lens sets for continuously changing the overall or meridional image size, or both, according to copending application Serial No. 713,701 filed March 2, 1934, or lenses from test sets of size lenses, for example according to copending application Serial No. 749,948, filed October 25, 1934.

Arrangements of this type are also inherently adapted for the performance of tests concerning the muscular defects known as phoria, and the so-called fusional amplitudes, as will be explained more in detail hereinafter.

In order successfully to carry out investigations of this character, it is necessary rigidly to position the eyes and the head not only during one test, but reproducibly for subsequent tests, and to adjust the instrument to fit the eyes of each particular patient. To this end, the distance between vertical axes v and w is adjustable for different pupillary distances, and means are provided to position the eyes so that their centers of rotation are actually located at the intersections of axes h, v and w, such means to be described in detail hereinafter. In order to assure measurable and exactly reproducible positioning of the eyes, a structure supporting the head at three points III, II, I! is provided, this head rest being universally adjustable by linear movement along three axes 1, 8, 9 and rotatory movement about these axes, as indicated by arrows. Six scales for measuring. these movements may be provided, as incorporated in one of the embodiments to be described hereinafter.

The size of an object observed by the patient may be expressed by the angles which rays com ing from certain points thereof subtend at the eyes, as for example angle p (Fig. 1) between lines from CD to F and point 2 on plane A, respectively. In order to determine image differences of the eyes according to the new method according to my invention, the eyes are caused to observe a means presenting to each eye the appearance of detail arranged in a certain manner relatively to its perception by each eye separately, and to a fixation point for both eyes. This means may, for example, be a shield in plane A with small practically point-like portions I, 2, 3, 4, which of course, forming one single pattern or detail, appear to both eyes similarly spaced, but to which is by some means imparted a character diiferent for each eye. Fig. 1 shows by way of example one method of accomplishing this result, and various structures for carrying out this method will be described in detail herein- 

